* {
    margin: 0;
}

.HolyGrail {
    display: flex;
    min-height: 100vh;
    flex-direction: column;
}

header {
    display: flex;
    flex: 0 0 3.5em;
    justify-content: flex-start;
    align-items: center;
    background-color: #004c8e;
    color: white;
}

header p span {
    display: block;
    margin-left: 9px;
    border-left: groove 1px rgba(255,255,255,0.5);
    padding-left: 11px;
    font-family: "日文毛笔字体";
}

footer {
    display: flex;
    flex: 0 0 3em;
    justify-content: center;
    align-items: center;
    color: white;
    background-color: #004c8e;
}

.HolyGrail-body {
    display: flex;
    flex: 10;
}

.HolyGrail-content {
    flex: 1 0;
}

.HolyGrail-nav {
    flex: 0 0 12em;
    order: -1;
    background-color: #5487a4;
}

/* 响应式布局再考虑 */
@media (max-width: 768px) {
    .HolyGrail-body {
        flex-direction: column;
        flex: 10;
    }
    .HolyGrail-content {
        flex: 1;
    }
    .HolyGrail-nav {
        flex: 0;
    }
}